CN105388348B - A kind of enhanced autobalance bridge and its method for realizing open-loop compensation - Google Patents
A kind of enhanced autobalance bridge and its method for realizing open-loop compensation Download PDFInfo
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- CN105388348B CN105388348B CN201510969716.7A CN201510969716A CN105388348B CN 105388348 B CN105388348 B CN 105388348B CN 201510969716 A CN201510969716 A CN 201510969716A CN 105388348 B CN105388348 B CN 105388348B
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- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
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Abstract
The invention discloses a kind of enhanced autobalance bridge and its methods for realizing open-loop compensation, belong to impedance measurement field, to interface and cable is measured including driving source, measured piece, voltmeter, range resistance, zero cross detection circuit, modulation-demodulation circuit, four ends, the present invention is using the feedback loop being made of zero cross detection circuit, modulation-demodulation circuit etc., autobalance bridge is enabled quickly and accurately to reach equilibrium state, has the characteristics that measuring speed is fast, high certainty of measurement；By disconnecting feedback loop, the amplitude loss of split ring status and phase offset are respectively calculated and compensate, and autobalance bridge is made to be rapidly achieved equilibrium state, improves measuring speed；In measurement frequency, measured material, cable is measured when measuring conditions change, and by performing the open-loop compensation of feedback loop, still autobalance bridge can be made to be rapidly achieved equilibrium state；Increase equilibrium state detection circuit, be rapidly achieved equilibrium state for autobalance bridge and strong guarantee is provided.
Description
Technical field
The invention belongs to impedance measurement fields, and in particular to a kind of enhanced autobalance bridge and its realize open-loop compensation
Method.
Background technology
Realize the measurement of the parameters such as the resistance R to measured piece, inductance L, capacitance C, quality factor q, loss factor D,
Core is exactly to carry out the measurement of impedance, and other parameters value can be extrapolated according to impedance value.At present, the method for realizing impedance measurement has
Many kinds, it is common to have bridge method, the resonance method, voltage-to-current method, RF voltage-to-currents method, Network Analysis Method and autobalance bridge
Method, each method have respective advantage and disadvantage, need to select different impedance measurement methods according to different application fields.Electric bridge
Method has a high certainty of measurement, at low cost, but measurement frequency narrow range, and needs to adjust bridge balance manually.The resonance method can be with
The measured piece with very high q value is measured, but measurement accuracy is low.Voltage-to-current method is suitable for probe type test needs, still
Measurement frequency range is limited by probe transformer.RF voltage-to-currents method has very high measurement frequency and measurement frequency model
Enclose, but measurement frequency be less than 100kHz when, cannot be in this way.Although Network Analysis Method is with very high measurement frequency
Rate, but occasion of the measured piece impedance for 50 Ω or so is only applicable to, therefore impedance measurement range is very narrow.It is situated between relative to above
Several impedance measurement methods to continue when requiring measurement frequency f >=20Hz, may be selected autobalance bridge method and realize that impedance is surveyed
Amount, with high certainty of measurement, measuring speed is fast, measurement frequency is high, impedance measurement range is wide the advantages that.
At present, conventional type autobalance bridge schematic diagram (as shown in Figure 1), using the short principle of void of operational amplifier, make by
The low side for surveying part is in " virtual earth " state, therefore can obtain Lp ends error current Id=0, i.e. Ix=Ir.Pass through voltmeter 1 and electricity
Pressure table 2 measures Vx and Vr values respectively, and Rr is range resistance value, is known all using high-precision, the measuring resistance of Low Drift Temperature
Amount, can thus calculate measured piece impedance value Zx.
Impedance measurement is realized using conventional type autobalance bridge method, has that design is simple, is easily achieved, but because by
It is limited to the characteristic of operational amplifier in itself, the general maximum of measurement frequency of conventional type autobalance bridge method can only achieve
100kHz in order to meet higher measurement frequency requirement, is improved on the basis of conventional type autobalance bridge method, obtains
A kind of enhanced autobalance bridge method (as shown in Figure 2), enhanced autobalance bridge method compare conventional type autobalance bridge
Method, the maximum feedback control loop difference lies in Lp ends are different, and conventional type autobalance bridge method only uses 1 operation amplifier
Device, and enhanced autobalance bridge method uses zero cross detection circuit, modulation-demodulation circuitry instead operational amplifier so that increase
The measurement frequency maximum of strong type autobalance bridge method can reach 110MHz, compared to conventional type autobalance bridge method, enhancing
The measurement frequency of type autobalance bridge method is largely improved.Although enhanced autobalance bridge method improves measurement
Frequency, but since enhanced autobalance bridge method increases the feedback control loops such as zero cross detection circuit, modulation-demodulation circuit,
Equilibrium state thus is rapidly achieved on autobalance bridge and produces influence so that the enhanced autobalance bridge side used at present
The problems such as method generally existing measuring speed is slow, measurement accuracy is low.
Invention content
For the above-mentioned problems in the prior art, the present invention proposes a kind of enhanced autobalance bridge and its realization
The method of open-loop compensation, reasonable design overcome the deficiencies in the prior art, have the characteristics that measuring speed is fast, high certainty of measurement.
To achieve these goals, the present invention adopts the following technical scheme that：
A kind of enhanced autobalance bridge, including driving source, measured piece, voltmeter, range resistance, zero cross detection circuit,
Modulation-demodulation circuit, four ends to interface and measure cable；
The driving source is configurable for providing excitation source signal for measured piece, including AC signal and direct current signal,
AC signal is generated by the first DDS；
The voltmeter includes first voltage table, second voltage table；
The first voltage table is configurable for carrying out voltage measurement to measured piece；
The second voltage table is configurable for carrying out voltage measurement to range resistance；
The range resistance, is configurable for the impedance ranges according to measured piece, selects suitable resistance gear；
Four end is respectively to encourage source Hc, measured piece measurement end Hp, range resistance terminal Lc, error current end to interface
Lp；
The driving source, voltmeter 1, range resistance, zero cross detection circuit correspond respectively to driving source of four ends to interface
Hold Hc, measured piece measurement end Hp, range resistance terminal Lc, error current end Lp；
The measurement cable includes the first measurement cable, the second measurement cable, third and measures cable and the 4th and measure cable；
The zero cross detection circuit is configurable for the error current Id of error current end Lp carrying out zero passage detection simultaneously
Carry out signal processing；
The modulation-demodulation circuit is configurable for that the signal that zero cross detection circuit exports is modulated and demodulated；
The third measures cable, zero cross detection circuit, modulation-demodulation circuit, range resistance and the 4th and measures cable shape
Into a feedback loop；
When autobalance bridge does not reach equilibrium state, error current by third measure cable, zero cross detection circuit,
Modulation-demodulation circuit, range resistance, the 4th measure cable, third measurement cable, recycle successively, form feedback loop, to negative
The open loop loss of feedback control loop compensates, and is closed feedback loop, autobalance bridge can reach equilibrium state.
Preferably, the zero cross detection circuit includes I/V conversion circuits, signal amplification circuit, ac-coupled circuit, first
D/A conversion circuits, signal amplification and filter circuit and balance state detection circuit, the I/V conversion circuits, signal amplification electricity
Road, ac-coupled circuit, the first D/A conversion circuits, signal amplification and filter circuit and balance state detection circuit pass through circuit
It is sequentially connected.
Preferably, the equilibrium state detection circuit, is configurable for whether detection autobalance bridge reaches equilibrium-like
State.
Preferably, the modulation-demodulation circuit includes 0 ° of direction circuit and 90 ° of direction circuits；
0 ° of direction circuit include the first multiplier, first integrator, the first variable gain amplifier, first switch,
First direct voltage source and third multiplier, one end of first multiplier, first integrator, the first variable gain amplifier
One end be sequentially connected by circuit；The other end of first variable gain amplifier and one end of third multiplier are opened by first
Connection connects；There are two contact, the other end of one of contact and the first variable gain amplifier connects for first switch setting
It connects, another contact is connected with one end of the first direct voltage source, the other end ground connection of first direct voltage source；
90 ° of direction circuits include the second multiplier, second integral device, the second variable gain amplifier, second switch,
Second direct voltage source and the 4th multiplier, one end of second multiplier, second integral device, the second variable gain amplifier
One end be sequentially connected by circuit；One end of the other end of second variable gain amplifier and the 4th multiplier is opened by second
Connection connects；There are two contact, the other end of one of contact and the second variable gain amplifier connects for second switch setting
It connects, another contact is connected with one end of the second direct voltage source, the other end ground connection of second direct voltage source；
The common end of the other end of the other end of first multiplier and the second multiplier composition is connected to zero cross detection circuit
Output terminal；The common end of the other end of the other end of third multiplier and the 4th multiplier composition is connected to range resistance and the
The common end of two voltmeters composition.
Preferably, 0 ° of direction circuit further includes the 2nd D/A conversion circuits, and the 2nd D/A conversion circuits are connected to
The input terminal of first integrator；90 ° of direction circuits further include the 3rd D/A conversion circuits, and the 3rd D/A conversion circuits connect
It is connected to the input terminal of second integral device.
Preferably, the modulation-demodulation circuit further includes third switch, the 4th switch, tertiary voltage table；The third is opened
It closes and one end of the 4th switch forms one end that common end is connected to tertiary voltage table, the other end ground connection of tertiary voltage table, institute
The other end for stating third switch is connected to the common end of third multiplier and the 4th multiplier composition, and the other end of the 4th switch connects
It is connected to the common end of the first multiplier and the second multiplier composition.
Preferably, the modulation-demodulation circuit further includes the 2nd DDS and negative circuit；
2nd DDS output first via reference signal V0 and the second tunnel reference signal V90 respectively to the first multiplier and
Second multiplier, first via reference signal V0 and the second tunnel reference signal V90 amplitudes are equal, frequency is equal, phase differs 90 °；
The first via reference signal V0 and the second tunnel reference signal V90 of 2nd DDS output, inverted circuit output the
Three tunnel reference signal V180 and the 4th tunnel reference signal V270 are respectively to third multiplier and the 4th multiplier, and third road is with reference to letter
Number V180 and the 4th tunnel reference signal V270 amplitudes are equal, frequency is equal, phase differs 90 °.
In addition, the present invention is it is also mentioned that a kind of open loop compensation approach of enhanced autobalance bridge, this method is using described
A kind of enhanced autobalance bridge, carries out in accordance with the following steps：
Step 1：Carry out the initial work of enhanced autobalance bridge；
Step 2：First switch and second switch are respectively turned on the first direct voltage source and the second direct voltage source, disconnected
The feedback loop of autobalance bridge makes the first direct voltage source and the second direct voltage source be respectively connected to third multiplier and
The input terminal of four multipliers；
Step 3：The output function of the first DDS is closed, the driving source output for making autobalance bridge is zero；Control the 2nd DDS
The way of output, export first via reference signal V0 and third road reference signal V180, the second tunnel reference signal V90 and the 4th
Road reference signal V270 is not exported；
Step 4：Using the output of third multiplier as the first Regulate signal of feedback loop, third switch is closed, the
Four switches disconnect, and the first Regulate signal is measured using tertiary voltage table, obtains the amplitude V1 and phase of the first Regulate signal
Position Φ 1；
Step 5：Under autobalance bridge feedback loop open loop situations, the first Regulate signal is flowed along feedback loop direction
Through a loop, using the output of zero cross detection circuit as the second Regulate signal, the 4th switch is closed, and third switch disconnects, profit
The second Regulate signal is measured with tertiary voltage table, obtains the amplitude V2 of the second Regulate signal and phase Φ 2；
Step 6：The amplitude for calculating feedback loop open loop is lost and compensates；By the first Regulate signal amplitude V1 and
The amplitude loss that the amplitude V2 of second Regulate signal can obtain feedback loop open loop is A0=V2/V1；For compensation open loop amplitude damage
A0 is consumed, by adjusting the first variable gain amplifier, the gain A 1 of the first variable gain amplifier is made to be set as open loop amplitude damage
The inverse of A0, i.e. A1=1/A0=V1/V2, and the gain A 2 of the second variable gain amplifier is consumed equal to the first variable gain to amplify
The gain A 1 of device；
Step 7：It calculates the phase offset of feedback loop open loop and compensates；When the phase of feedback loop open loop is inclined
It moves when being 180 °, autobalance bridge can be rapidly achieved equilibrium state, by 1 and second Regulate signals of phase Φ of the first Regulate signal
Phase Φ 2 can obtain feedback loop open loop phase offset be Φ=Φ 2- Φ 1；Φ is deviated for compensation open loop phase, relatively
In the phase of the first DDS output signals of driving source, the phase of the 2nd DDS output reference signals is adjusted, by preset to the 2nd DDS
One phase offset α, and phase offset α preset the 2nd DDS=Φ -180 °；
Step 8：First switch and second switch are respectively turned on the first variable gain amplifier and the amplification of the second variable gain
Device is closed the feedback loop of autobalance bridge, and third switch and the 4th switch are all off, open the output work of the first DDS
Can, make the driving source output voltage signal of autobalance bridge, control the way of output of the 2nd DDS, make first via reference signal V0,
Second tunnel reference signal V90, third road reference signal V180 and the 4th tunnel reference signal V270 output voltage signals；
Step 9：By the equilibrium state detection circuit of autobalance bridge, judge whether autobalance bridge reaches equilibrium-like
State；
If：Judging result is that autobalance bridge does not reach equilibrium state, then performs step 2~8；
Or judging result is that autobalance bridge reaches equilibrium state, then terminates to detect.
In addition, the present invention is it is also mentioned that a kind of impedance measurement method, this method use a kind of above-mentioned enhanced autobalance
Bridge after autobalance bridge reaches equilibrium state, carries out in accordance with the following steps：
Step 1：Voltage measurement is carried out to voltage signal by first voltage table and second voltage table；
Step 2：According to formulaCalculate the impedance value Zx of measured piece；In formula, Rr is range resistance value, and
Range resistance all using high-precision, the measuring resistance of Low Drift Temperature, Vx and Vr are respectively that first voltage table and second voltage table are surveyed
The voltage signal values of amount.
The principle of the present invention is：
Enhanced autobalance bridge uses four ends to output interface, including Hc ends, Hp ends, Lp ends and Lc ends.Hc is excitation
Source, including AC signal and direct current signal, wherein AC signal realizes that direct current signal is turned using the D/A of 16bit using DDS1
Parallel operation is realized, AC signal and direct current is superimposed, after signal drive circuit is handled, is applied on measured piece DUT.Hp is
The high-end voltage measurement end of measured piece, measures voltage Vx on measured piece.Lc is range resistance terminal, according to measured piece impedance model
It encloses, selects corresponding range resistance gear, and voltage Vr on range resistance Rr is measured, and range resistance is all using height
Precision, the measuring resistance of Low Drift Temperature.Lp is error current end, and error current Id is equal on measured piece on electric current Ix and range resistance
The difference of electric current Ir.
When autobalance bridge does not reach equilibrium state, i.e. the error current Id at Lp ends is not equal to zero, error current Id
Cable, zero cross detection circuit, modulation-demodulation circuit, range resistance, Lc ends measurement cable, Lp ends measurement electricity are measured by Lp ends
Cable recycles successively, forms feedback loop LOOP.Autobalance bridge is made quickly and accurately to reach equilibrium state, is needed to negative
The open loop loss of feedback control loop compensates.After feedback loop is disconnected, the amplitude loss of divided ring and phase offset difference
It is computed and compensated for.After completing compensation to the open loop situations of feedback loop, feedback loop is closed, autobalance bridge is reachable
To equilibrium state, at this moment the error current Id at Lp ends is equal to zero, and therefore, measured piece low side is known as " virtual earth " of autobalance bridge
Point.
After autobalance bridge reaches equilibrium state, Lp ends error current Id is zero, i.e. Ix=Ir, therefore the resistance of measured piece
Anti- value Zx is：
In formula (1), Rr is range resistance value, and range resistance all using in high precision, the measuring resistance of Low Drift Temperature,
For known quantity, Vx and Vr are to be measured, therefore, the impedance value Zx of measured piece can be calculated by formula (1).
Advantageous effects caused by the present invention：
The present invention proposes a kind of enhanced autobalance bridge and its method for realizing open-loop compensation, with prior art phase
Than the present invention is had using the feedback loop being made of the part such as zero cross detection circuit, modulation-demodulation circuit, range resistance
The features such as measuring speed is fast, high certainty of measurement；DDS is used to provide reference signal for modulation-demodulation circuit, accurately realizes two-way
Reference signal phase differs 90 °；By disconnecting feedback loop, the amplitude loss of split ring status and phase offset carry out respectively
It computes and compensates for, autobalance bridge is made to be rapidly achieved equilibrium state, improve measuring speed；In measurement frequency, measured material, measurement
Cable is when measuring conditions change, and by performing the open-loop compensation of feedback loop, autobalance bridge can still be rapidly achieved flat
Weighing apparatus state；Increase the equilibrium state detection circuit of autobalance bridge, detection is provided for whether autobalance bridge reaches equilibrium state
Means provide strong guarantee so as to be rapidly achieved equilibrium state for autobalance bridge.
Description of the drawings
Fig. 1 is the schematic diagram of conventional type autobalance bridge.
Fig. 2 is a kind of schematic diagram of enhanced autobalance bridge.
Fig. 3 is the schematic diagram of zero cross detection circuit in a kind of enhanced autobalance bridge of the present invention.
Fig. 4 is the schematic diagram of modulation-demodulation circuit in a kind of enhanced autobalance bridge of the present invention.
Fig. 5 is a kind of schematic diagram of enhanced autobalance bridge open-loop compensation of the present invention.
Fig. 6 is a kind of flow diagram of enhanced autobalance bridge open loop compensation approach of the present invention.
Fig. 7 is a kind of schematic diagram that impedance measurement is realized using enhanced autobalance bridge of the present invention.
Fig. 8 is a kind of flow diagram that impedance measurement is realized using enhanced autobalance bridge of the present invention.
Specific embodiment
Below in conjunction with the accompanying drawings and specific embodiment is described in further detail the present invention：
Embodiment 1：
As shown in Fig. 2, enhanced autobalance bridge, including driving source, measured piece, voltmeter 1, voltmeter 2, range electricity
Resistance, zero cross detection circuit, modulation-demodulation circuit, four ends to interface and measure cable.Do not reach equilibrium-like in autobalance bridge
During state, Lp ends error current Id by Lp ends measure cable → zero cross detection circuit → modulation-demodulation circuit → range resistance →
Lc ends measure cable → Lp ends and measure cable →... ..., recycle successively, form feedback loop LOOP.
As shown in figure 3, zero cross detection circuit, mainly include I/V conversion circuits, signal amplification circuit, ac-coupled circuit,
D/A conversion circuits N1, signal amplification and filter circuit and balance state detection circuit.When autobalance bridge does not reach equilibrium-like
Error current Id when Lp ends error current Id is not zero, is first sent to I/V conversion circuits, is converted into voltage signal, and pass through by state
Signal amplification circuit processing, then by ac-coupled circuit, filter out direct current signal, only retain AC signal, utilize D/A converter
N1 provides DC bias signal for A points, makes the output signal of zero cross detection circuit, i.e. the direct current signal of B points is zero.A points are believed
Number after amplification and filter circuit processing, before modulation-demodulation circuit, in the flat of one autobalance bridge of B point designs
Weigh state detection circuit, when autobalance bridge reaches equilibrium state, equilibrium state detection circuit output high level, on the contrary output
Low level, the state value of equilibrium state detection circuit output are sent in FPGA and are judged and handled, be autobalance bridge whether
Reach equilibrium state and detection means is provided.
As shown in figure 4, modulation-demodulation circuit, is mainly made of 0 ° of direction circuit and 90 ° of direction circuits, specifically includes and multiply
Musical instruments used in a Buddhist or Taoist mass 1, multiplier 2, multiplier 3, multiplier 4, integrator 1, integrator 2, D/A converter N2, D/A converter N3, variable increasing
Beneficial amplifier VA1, variable gain amplifier VA2, direct voltage source DC1, direct voltage source DC2, switch S1, switch S2, DDS2
And negative circuit.
DDS2 exports 2 tunnel reference signal V0 and V90, and V0 and V90 must be kept that amplitude is equal, frequency is equal, phase phase
Poor 90 °, V0 and V90 export other 2 tunnel reference signal V180 and V270, and V180 and V270 are equally necessary by negative circuit
Holding amplitude is equal, frequency is equal, phase differs 90 °, this 4 tunnel reference signal gives 4 multiplier inputs respectively.
Lp ends error current Id gives multiplier 1 He respectively after zero cross detection circuit is handled, by B point input signals Vi
The input terminal of multiplier 2, is multiplied respectively with reference signal V0, V90.If input signal Vi=xsin (ω t+ α) is set, with reference to letter
Number V0=ysin (ω t+ β), can obtain：
DC component is included in the output signal of multiplier 1 it can be seen from formula (2)With exchange point
Amount
The output signal of multiplier 1 gives integrator 1, i.e., formula (2) is integrated and can obtained：
It is π xycos (alpha-beta) only to include DC component after the processing of integrator 1, in output signal, and AC compounent
It is zero, this DC component is exactly components of the input signal Vi on reference signal V0, similarly can obtain input signal Vi and is joining
The component on signal V90 is examined, thereby realizes the demodulation function of input signal Vi.
In the integrator circuit of modulation-demodulation circuit, also comprising D/A converter N2 and D/A converter N3, direct current is exported
Signal, the respectively input terminal of integrator 1 and integrator 2 provide certain DC bias signal.Integrator 1 and integrator 2 are defeated
The direct current signal gone out send respectively to variable gain amplifier VA1 and variable gain amplifier VA2, exports direct current signal respectively.
When performing impedance measurement, switch S1 and switch S2 get to A points respectively, make variable gain amplifier VA1 and variable gain amplifier
The direct current signal of VA2 outputs send input terminal to multiplier 3 and multiplier 4 respectively, respectively with reference signal V180, V270 phase
Multiply.If the direct current signal for setting variable gain amplifier VA1 and VA2 output is respectively M and N, due to reference signal V0=ysin
(ω t+ β), then can obtain reference signal V180=asin (+180 ° of ω t+ β), reference signal V270=bsin (ω t+ β+
270 °), therefore the output signal of multiplier 3 is MV180, the output signal of multiplier 4 is NV270.Multiplier 3 is exported
Signal is added and can obtain with 4 output signal of multiplier：
It can be seen that by formula (4)：After 3 output signal of multiplier is added with 4 output signal of multiplier, obtained C points are defeated
Going out signal isIts frequency is equal to measurement frequency, thereby realizes input signal Vi
Modulation function.
Embodiment 2：
On the basis of above-described embodiment 1, with reference to shown in Fig. 5, the present invention proposes a kind of enhanced autobalance bridge
Open loop compensation approach will make autobalance bridge quickly and accurately reach equilibrium state, need to disconnect enhanced autobalance bridge
Feedback loop, the amplitude loss of split ring status and phase offset are respectively calculated and compensate, specific to perform flow such as Fig. 6
It is shown.
Step 1：The initial work of enhanced autobalance bridge is performed, mainly includes the output of DDS signals, the choosing of range resistance
Select, amplitude gain selection, filter circuit selection, integrating capacitor selection, on off state selection etc.；
Step 2：Switch S1 and switch S2 get to B points respectively, connect direct voltage source DC1 and DC2, disconnect autobalance bridge
Feedback loop, direct voltage source DC1 and direct voltage source DC2 is made to be coupled with the input terminal of multiplier 3 and multiplier 4；
Step 3：DDS1 output functions are closed, the driving source output for making autobalance bridge is zero, so as to obtain autobalance
The high-end of bridge is ground level；The DDS2 way of outputs are controlled, open 1 output function of channel, is i.e. V0, V180 is exported, and closing passage 2 is defeated
Go out function, i.e. V90, V270 is not exported；
Step 4：Using the output of multiplier 3 as the Regulate signal 1 of feedback loop, switch S3 is closed, and switch S4 is disconnected,
Regulate signal 1 is measured using voltmeter 3, the amplitude V1 of adjusted signal 1 and phase Φ 1；
Step 5：Under autobalance bridge feedback loop open loop situations, Regulate signal 1 is along feedback loop LOOP directions
A loop is flowed through, using the output of zero cross detection circuit as Regulate signal 2, switch S4 is closed, and switch S3 is disconnected, and utilizes voltage
Table 3 measures Regulate signal 2, the amplitude V2 of adjusted signal 2 and phase Φ 2；
Step 6：The amplitude for calculating feedback loop open loop is lost and compensates；By the amplitude V1 and tune of Regulate signal 1
The amplitude loss that the amplitude V2 of section signal 2 can obtain feedback loop open loop is A0=V2/V1；A0 is lost for compensation open loop amplitude,
By adjusting variable gain amplifier VA1, the gain A 1 of variable gain amplifier VA1 is made to be set as falling for open loop amplitude loss A0
Number, i.e. A1=1/A0=V1/V2, and the gain A 2 of variable gain amplifier VA2 are equal to the gain of variable gain amplifier VA1
A1；
Step 7：It calculates the phase offset of feedback loop open loop and compensates；When the phase of feedback loop open loop is inclined
It moves when being 180 °, autobalance bridge can be rapidly achieved equilibrium state, by the phase Φ 1 of Regulate signal 1 and the phase of Regulate signal 2
The phase offset that Φ 2 can obtain feedback loop open loop is Φ=Φ 2- Φ 1；Φ is deviated for compensation open loop phase, relative to excitation
The phase of source DDS1 output signals adjusts the phase of DDS2 output signals, by a phase offset α preset to DDS2, and
Phase offset α preset DDS2=Φ -180 °；
Step 8：Switch S1 and switch S2 get to A points respectively, are closed the feedback loop of autobalance bridge, switch S3 and open
It is all off to close S4, opens DDS1 output functions, makes the driving source output voltage signal of autobalance bridge.Control DDS2 output sides
Formula opens 2 output function of channel 1 and channel, i.e. V0, V90, V180, V270 output voltage signal；
Step 9：By the equilibrium state detection circuit of autobalance bridge, judge whether autobalance bridge reaches equilibrium-like
State；
If：Judging result is that autobalance bridge does not reach equilibrium state, then performs step 2~8, recalculate negative-feedback
The open loop amplitude loss of loop and phase offset simultaneously compensate；
Or autobalance bridge reaches equilibrium state, then terminates to detect, perform down, starts to perform impedance measurement work.
Embodiment 3：
On the basis of above-described embodiment 1 and embodiment 2, after autobalance bridge reaches equilibrium state, resistance is proceeded by
Anti- measurement, with reference to impedance measurement principle figure shown in Fig. 7, specific execution flow is as shown in Figure 8.
Step 1：Switch S5 is got into A, voltage signal Vx is measured；
Step 2：Switch S5 is got into B, voltage signal Vr is measured；
Step 3：It is described according to formula (1)Calculate the impedance value Zx of measured piece, in formula, Rr is amount
Journey resistance value, and range resistance is all using high-precision, the measuring resistance of Low Drift Temperature.
The present invention proposes a kind of enhanced autobalance bridge and its method for realizing open-loop compensation, using by zero passage detection
The feedback loop of the part such as circuit, modulation-demodulation circuit, range resistance composition so that autobalance bridge can quickly, accurately
Ground reaches equilibrium state, has the characteristics that measuring speed is fast, high certainty of measurement；DDS is used to provide reference for modulation-demodulation circuit
Signal accurately realizes that two-way reference signal phase differs 90 °；By disconnecting feedback loop, the amplitude damage of split ring status
Consumption and phase offset are respectively calculated and compensate, and autobalance bridge is made to be rapidly achieved equilibrium state, improve measuring speed；It is surveying
It measures frequency, measured material, measure cable when measuring conditions change, by performing the open-loop compensation of feedback loop, can still make
Autobalance bridge is rapidly achieved equilibrium state；Increase autobalance bridge equilibrium state detection circuit, be autobalance bridge whether
Reach equilibrium state and detection means is provided, strong guarantee is provided so as to be rapidly achieved equilibrium state for autobalance bridge.
Certainly, above description is not limitation of the present invention, and the present invention is also not limited to the example above, this technology neck
The variations, modifications, additions or substitutions that the technical staff in domain is made in the essential scope of the present invention should also belong to the present invention's
Protection domain.
Claims (7)
1. a kind of enhanced autobalance bridge, it is characterised in that：Including driving source, measured piece, voltmeter, range resistance, zero passage
Detection circuit, modulation-demodulation circuit, four ends to interface and measure cable；
The driving source is configurable for providing excitation source signal for measured piece, including AC signal and direct current signal, exchange
Signal is generated by the first DDS；
The voltmeter includes first voltage table, second voltage table；
The first voltage table is configurable for carrying out voltage measurement to measured piece；
The second voltage table is configurable for carrying out voltage measurement to range resistance；
The range resistance, is configurable for the impedance ranges according to measured piece, selects suitable resistance gear；
Four end is respectively to encourage source, measured piece measurement end, range resistance terminal, error current end to interface；
The driving source, first voltage table, range resistance, zero cross detection circuit correspond respectively to driving source of four ends to interface
End, measured piece measurement end, range resistance terminal, error current end；
The measurement cable includes the first measurement cable, the second measurement cable, third and measures cable and the 4th and measure cable；
The zero cross detection circuit is configurable for the error current at error current end carrying out zero passage detection and carries out signal
Processing；
The modulation-demodulation circuit is configurable for that the signal that zero cross detection circuit exports is modulated and demodulated；
The third measures cable, zero cross detection circuit, modulation-demodulation circuit, range resistance and the 4th and measures cable formation one
A feedback loop；
When autobalance bridge does not reach equilibrium state, error current measures cable, zero cross detection circuit, tune by third
System-demodulator circuit, range resistance, the 4th measure cable, third measurement cable, recycle successively, form feedback loop, to negative anti-
The open loop loss of feedback loop compensates, and is closed feedback loop, autobalance bridge can reach equilibrium state；Modulation-the solution
Circuit is adjusted to include 0 ° of direction circuit and 90 ° of direction circuits；
0 ° of direction circuit includes the first multiplier, first integrator, the first variable gain amplifier, first switch, first
Direct voltage source and third multiplier, one end of first multiplier, first integrator, the first variable gain amplifier one
End is sequentially connected by circuit；The other end of first variable gain amplifier and one end of third multiplier are connected by first switch
It connects；The first switch setting is there are two contact, and one of contact is connected with the other end of the first variable gain amplifier, separately
One contact is connected with one end of the first direct voltage source, the other end ground connection of first direct voltage source；
90 ° of direction circuits include the second multiplier, second integral device, the second variable gain amplifier, second switch, second
Direct voltage source and the 4th multiplier, one end of second multiplier, second integral device, the second variable gain amplifier one
End is sequentially connected by circuit；One end of the other end of second variable gain amplifier and the 4th multiplier is connected by second switch
It connects；The second switch setting is there are two contact, and one of contact is connected with the other end of the second variable gain amplifier, separately
One contact is connected with one end of the second direct voltage source, the other end ground connection of second direct voltage source；
The common end of the other end of the other end of first multiplier and the second multiplier composition is connected to the defeated of zero cross detection circuit
Outlet；The common end of the other end of the other end of third multiplier and the 4th multiplier composition is connected to range resistance and the second electricity
Press the common end of table composition；The modulation-demodulation circuit further includes third switch, the 4th switch, tertiary voltage table；The third
One end composition common end of switch and the 4th switch is connected to one end of tertiary voltage table, and the other end of tertiary voltage table is grounded,
The other end of the third switch is connected to the common end of third multiplier and the 4th multiplier composition, the other end of the 4th switch
It is connected to the common end of the first multiplier and the second multiplier composition.
2. enhanced autobalance bridge according to claim 1, it is characterised in that：The zero cross detection circuit includes I/V
Conversion circuit, signal amplification circuit, ac-coupled circuit, the first D/A conversion circuits, signal amplification and filter circuit and equilibrium-like
State detection circuit, the I/V conversion circuits, signal amplification circuit, ac-coupled circuit, the first D/A conversion circuits, signal amplification
And filter circuit and balance state detection circuit are sequentially connected by circuit.
3. enhanced autobalance bridge according to claim 2, it is characterised in that：The equilibrium state detection circuit, quilt
It is configured for whether detection autobalance bridge reaches equilibrium state.
4. enhanced autobalance bridge according to claim 1, it is characterised in that：0 ° of direction circuit further includes second
D/A conversion circuits, the 2nd D/A conversion circuits are connected to the input terminal of first integrator；90 ° of direction circuits further include
3rd D/A conversion circuits, the 3rd D/A conversion circuits are connected to the input terminal of second integral device.
5. enhanced autobalance bridge according to claim 1, it is characterised in that：The modulation-demodulation circuit further includes
2nd DDS and negative circuit；
The 2nd DDS output first via reference signals and the second tunnel reference signal are respectively to the first multiplier and the second multiplication
Device, first via reference signal and the second tunnel reference signal amplitude are equal, frequency is equal, phase differs 90 °；
The first via reference signal and the second tunnel reference signal of the 2nd DDS outputs, inverted circuit output third road reference
Signal and the 4th tunnel reference signal are respectively to third multiplier and the 4th multiplier, and third road reference signal and the 4th tunnel are with reference to letter
Number amplitude is equal, frequency is equal, phase differs 90 °.
6. a kind of open loop compensation approach of enhanced autobalance bridge, it is characterised in that：Using one kind as claimed in claim 5
Enhanced autobalance bridge, carries out in accordance with the following steps：
Step 1：Carry out the initial work of enhanced autobalance bridge；
Step 2：First switch and second switch are respectively turned on the first direct voltage source and the second direct voltage source, disconnected automatic
The feedback loop of balance bridge makes the first direct voltage source and the second direct voltage source be respectively connected to third multiplier and the 4th and multiply
The input terminal of musical instruments used in a Buddhist or Taoist mass；
Step 3：The output function of the first DDS is closed, the driving source output for making autobalance bridge is zero；Control that the 2nd DDS's is defeated
Go out mode, export first via reference signal and third road reference signal, the second tunnel reference signal and the 4th tunnel reference signal are not
Output；
Step 4：Using the output of third multiplier as the first Regulate signal of feedback loop, third switch is closed, and the 4th opens
Shutdown is opened, and the first Regulate signal is measured using tertiary voltage table, obtains the amplitude V1 of the first Regulate signal and phase Φ
1；
Step 5：Under autobalance bridge feedback loop open loop situations, the first Regulate signal flows through one along feedback loop direction
A loop, using the output of zero cross detection circuit as the second Regulate signal, the 4th switch is closed, and third switch disconnects, and utilizes the
Three voltmeters measure the second Regulate signal, obtain the amplitude V2 of the second Regulate signal and phase Φ 2；
Step 6：The amplitude for calculating feedback loop open loop is lost and compensates；By the amplitude V1 of the first Regulate signal and second
The amplitude loss that the amplitude V2 of Regulate signal can obtain feedback loop open loop is A0=V2/V1；A0 is lost for compensation open loop amplitude,
By adjusting the first variable gain amplifier, the gain A 1 of the first variable gain amplifier is made to be set as open loop amplitude loss A0's
Inverse, i.e. A1=1/A0=V1/V2, and the gain A 2 of the second variable gain amplifier is equal to the increasing of the first variable gain amplifier
Beneficial A1；
Step 7：It calculates the phase offset of feedback loop open loop and compensates；When the phase offset of feedback loop open loop is
At 180 °, autobalance bridge can be rapidly achieved equilibrium state, by the phase of 1 and second Regulate signals of phase Φ of the first Regulate signal
The phase offset that position Φ 2 can obtain feedback loop open loop is Φ=Φ 2- Φ 1；Φ is deviated for compensation open loop phase, relative to sharp
The phase of the first DDS output signals of source is encouraged, the phase of the 2nd DDS output reference signals is adjusted, by preset one to the 2nd DDS
Phase offset α, and phase offset α preset the 2nd DDS=Φ -180 °；
Step 8：First switch and second switch are respectively turned on the first variable gain amplifier and the second variable gain amplifier, close
The feedback loop of autobalance bridge is closed, third switch and the 4th switch are all off, open the output function of the first DDS, make
The driving source output voltage signal of autobalance bridge controls the way of output of the 2nd DDS, makes first via reference signal, the second tunnel
Reference signal, the output of third road reference signal and the 4th tunnel reference signal output voltage signal；
Step 9：By the equilibrium state detection circuit of autobalance bridge, judge whether autobalance bridge reaches equilibrium state；
If：Judging result is that autobalance bridge does not reach equilibrium state, then performs step 2~8；
Or judging result is that autobalance bridge reaches equilibrium state, then terminates to detect.
7. a kind of impedance measurement method, using a kind of enhanced autobalance bridge as described in claim 1, in autobalance bridge
After reaching equilibrium state, carry out in accordance with the following steps：
Step 1：Voltage measurement is carried out to voltage signal by first voltage table and second voltage table；
Step 2：According to formulaCalculate the impedance value Zx of measured piece；In formula, Rr is range resistance value, and range
For resistance all using high-precision, the measuring resistance of Low Drift Temperature, Vx and Vr are respectively that first voltage table and second voltage table measure
Voltage signal values.
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| CN106066425B (en) * | 2016-07-29 | 2019-01-08 | 中国电子科技集团公司第四十一研究所 | A kind of impedance measurement device and its method for realizing compensation for calibrating errors |
| CN110596559B (en) * | 2019-10-12 | 2021-08-03 | 积成电子股份有限公司 | Time-sharing grounding multi-balance bridge-based direct current bus and feeder line monitoring method |
| CN112130001B (en) * | 2020-11-19 | 2021-02-26 | 佛山市联动科技股份有限公司 | LCR impedance test equipment |
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| CN102662109B (en) * | 2012-04-16 | 2014-07-02 | 上海电机学院 | Balanced bridge |
| CN105044465B (en) * | 2015-07-10 | 2018-01-02 | 厦门大学 | The method of autobalance bridge and measurement DUT impedances based on the double DDS of synchronised clock |
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